The default behavior is for OMV to notify once used disk space reaches 80% of capacity. Many find this value too low and the frequent notifications annoying.
To raise the notification threshold above the default 80% value, to 95% for example, perform the following:
As the root user, edit the file: /etc/default/openmediavault and add the following line (or change it to the value you want if it already exists):
OMV_MONIT_SERVICE_FILESYSTEM_SPACEUSAGE=95
Run the following commands as root in the shell:
For OMV 2.x:
/etc/init.d/openmediavault-engined restart
omv-mkconf monit
/etc/init.d/monit restart
For OMV 3.x and 4.x :
omv-mkconf monit
monit reload
For OMV 5.x:
omv-salt stage run prepare
omv-salt deploy run monit